1. Field of the Invention
The present invention relates to air presses for a papermaking machine, and, more particularly, to end seal arrangements therefor.
2. Description of the Related Art
Effective water removal from a paper web is essential to the papermaking process. Various types of presses, using some combination of juxtaposed rolls, have been used for some time now for water removal. Such presses rely on the hydraulic pressure created at the nip between each pair of juxtaposed rolls through which the paper web travels in a given press configuration to drive water from the paper web.
Various press have been developed which have attempted to add an element of a positive air pressure within the press assembly to more effectively force the water from the paper web. With respect to roll presses specifically, the rolls of the press have been configured to form a chamber with a positive air pressure being supplied therewithin.
However, the effectiveness of a multi-roll air presses is limited by the degree to which the air chamber thereof can be sealed. The areas of the press where sealing becomes quite crucial are those areas where the paper web and the membrane(s) carrying it do not pass, as the web/membrane(s) combination inherently acts to seal the region of each nip through which it passes. Those regions of the air press through which the paper web/membrane(s) combination does not pass are the opposed lateral ends of each nip and the opposed chamber ends defined by the two sets of roll end associated with the air press. Consequently, an end seal mechanism is provided at each chamber end, each such mechanism having a seal member which contacts each of the roll ends associated with that particular chamber end.
The ability of the end seal mechanism to efficiently seal a chamber is predicated on the application of a sufficient sealing force so that the seal member thereof maintains sealing contact with each of the roll ends of that chamber end. On the other hand, applying a force thereto that is greater than that needed to maintain a seal will cause the seal member to wear out quicker than is necessary.
Additionally, current end seal mechanisms do not facilitate adjustments in the positioning thereof or in the force ultimately applied on the seal member thereof With such systems, retraction of the end seal mechanisms for start-up and/or maintenance is not readily achieved. Additionally, it is difficult to optimize the forces applied to the seal member during start-up to initially achieve a sufficient seal therewith and yet promote a long life thereof.
What is needed in the art is an end seal mechanism in which the sealing force applied to the seal member thereof can be readily adjusted in order to achieve sufficient sealing while minimizing the rate of wear of the seal member; and an end seal mechanism which permits adjustments in the positioning thereof and in the amount of force placed upon the seal member thereof during various operational stages.
The present invention provides an end seal mechanism for an air press of a papermaking machine in which the force applied upon the end seal mechanism is independent of the air pressure inside the air press, the sealing force placed thereupon and the position thereof instead being controlled by an adjustable bias mechanism.
The invention comprises, in one form thereof, an air press for pressing a fiber web, the air press including a plurality of rolls and a pair of end seal arrangements. Of the plurality of rolls, each pair of adjacent rolls forms a nip therebetween. Further, each roll has a pair of roll ends, the plurality of rolls together forming two sets of roll ends. Each end seal arrangement coacts with one set of roll ends, the plurality of rolls and the pair of end seal arrangements together defining an air press chamber having an air chamber pressure. Each end seal arrangement is composed of at least one roll seal, including a first roll seal, and an adjustable bias mechanism. Each roll seal forms a seal with at least one roll end, and one side of the first roll seal being exposed to the air chamber pressure. The adjustable bias mechanism is configured for controlling a position of each roll seal relative to a respective at least one roll end and for adjusting a seal force between the roll seal and the respective at least one roll end.
In another form, the present invention comprises a method of achieving an end seal in an air press for pressing a paper web. The method includes a series of steps, the first of which is providing a plurality of rolls, each pair of adjacent rolls forming a nip therebetween. Each roll has a pair of roll ends, the plurality of rolls together forming two sets of roll ends. An end seal arrangement is positioned adjacent a respective set of roll ends, the plurality of rolls and the respectively positioned end seal arrangements together defining an air press chamber having an air chamber pressure. Each end seal arrangement is composed of at least one roll seal, including a first roll seal, and an adjustable bias mechanism. Each roll seal forms a seal with at least one roll end, and one side of the first roll seal being exposed to the air chamber pressure. The adjustable bias mechanism is configured for controlling a position of each roll seal relative to a respective at least one roll end and for adjusting a seal force between the roll seal and the respective at least one roll end. The seal force provided by the adjustable bias mechanism is increased to seat the set of roll ends within the end seal arrangement. Then, the seal force provided by the adjustable bias mechanism is decreased upon seating of the set of roll ends within the end seal arrangement. Finally, a substantially constant low net force is maintained on each roll seal upon the seating and during operation of the air press, the substantially constant low net force being maintained using the adjustable bias mechanism.
an end seal mechanism in which the sealing force applied to the seal member thereof can be readily adjusted in order to achieve sufficient sealing while minimizing the rate of wear of the seal member; and an end seal mechanism which permits adjustments in the positioning thereof and in the amount of force placed upon the seal member thereof during various operational stages.
An advantage of the present invention is the seal force applied to the seal member of the end seal mechanism can be readily adjusted in order to achieve sufficient sealing while minimizing the rate of wear of the seal member.
Another advantage is the end seal mechanism permits adjustments in the positioning thereof and in the amount of force placed upon the seal member thereof during various operational stages, thereby facilitating the optimization of both the forces applied to the seal member during start-up to initially achieve a sufficient seal therewith and the force needed to promote a long life thereof.
Yet another advantage is that the end seal mechanism can be designed so that the total force applied on a seal member is independent of the air chamber pressure in the air press and thus not subject to potential fluctuations in the air chamber pressure.
An even further advantage is that biasing springs can be eliminated from the design of the end seal mechanism due to the presence of the adjustable bias mechanism.